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// Copyright 2018 The gVisor Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//go:build linux
// +build linux
// Package tun contains methods to open TAP and TUN devices.
package tun
import (
"unsafe"
"golang.org/x/sys/unix"
)
// Open opens the specified TUN device, sets it to non-blocking mode, and
// returns its file descriptor.
func Open(name string) (int, error) {
return open(name, unix.IFF_TUN|unix.IFF_NO_PI)
}
// OpenTAP opens the specified TAP device, sets it to non-blocking mode, and
// returns its file descriptor.
func OpenTAP(name string) (int, error) {
return open(name, unix.IFF_TAP|unix.IFF_NO_PI)
}
func open(name string, flags uint16) (int, error) {
fd, err := unix.Open("/dev/net/tun", unix.O_RDWR, 0)
if err != nil {
return -1, err
}
var ifr struct {
name [16]byte
flags uint16
_ [22]byte
}
copy(ifr.name[:], name)
ifr.flags = flags
_, _, errno := unix.Syscall(unix.SYS_IOCTL, uintptr(fd), unix.TUNSETIFF, uintptr(unsafe.Pointer(&ifr)))
if errno != 0 {
unix.Close(fd)
return -1, errno
}
if err = unix.SetNonblock(fd, true); err != nil {
unix.Close(fd)
return -1, err
}
return fd, nil
}
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